... what should we do?
I guess it all depends on how it would be implemented, which is something I have a hard time imagining at this moment.
How do you imagine day to day online life in a post-Chat Control EU world? Which ways of communicating would still be private? Is there anything we can do at this point to prepare for the worst outcome?
Chat control is more of a threat for the less tech literate masses. It will have to be implemented client and / or server side. If you use foss software it's basically impossible to enforce chat control, because some dude in his basement can always fork any project that may get targeted by it. If you're privacy conscious and using linux, degoogled android and decentralized messengers you're already out of reach of chat control.
Which doesn't mean that it isn't a threat and we shouldn't fight it.
This is what I don't understand, how will the EU enforce Chat Control when we can use software that doesn't implement backdoors? Maybe the EU will be happy to get the majority of messages from the mainstream proprietary apps, but what if they want to get the rest too? I'm worried that this will lead to very bad places. Could they ban F-Droid? Will I end up on a list if I use unauthorized software? Who knows.
My fear is that they will start off by applying this to Messenger, WhatsApp etc.
Then, in a few years, when criminals and tech-savvy people move to XMPP etc, they will say "the laws aren't working, we need to apply it at the OS level instead", and since iOS and Android have a big market share it's very easy for them to do it.
At that point, trying to communicate with friends becomes very hard. It's one thing to get them to switch apps, but asking them to switch phone or OS is a whole other hurdle.
I'm trying to contribute both code and money to make XMPP, and mobile linux as good as possible before that can happen. I feel we need to buy time, by delaying and delaying chat control as much as possible, to make the free software, federated systems better and appealing to regular people. And then we can use that technology to buy time to push for political changes. I feel the only long-term solution here will be a political, rather than technical one.
It all feels like an impossible task, but I feel all we can do is try as hard as we can to make the world more like the one we want.
Briar is the messaging app I would switch to. It was designed for protesters. No central servers, peer-to-peer, defaults to sending messages through tor, it can also send using wifi, data, or bluetooth.